Ion Rutherford Backscattering Research Articles

W diffusion in paramagnetic and ferromagnetic α-Fe

Diffusion of W in the 723–1153 K temperature range both in paramagnetic and ferromagnetic α-Fe was studied, diffusion couples were manufactured by W evaporation onto high-purity Fe samples. Measurements were made using the Heavy Ion Rutherford Backscattering (HIRBS) technique as the analysis tool. A straight Arrhenius plot was obtained in the paramagnetic region with a break at the Curie temperature (1043 K) followed by a curved plot at lower temperatures as a product of the effect of ferromagnetism on diffusion. A straight Arrhenius plot was obtained in the paramagnetic region with a break at the Curie temperature (1043 K) followed by a curved plot at lower temperatures resulting from the effect of ferromagnetism on diffusion. A previous developed model for the diffusion of non-magnetic impurities in ferromagnetic Fe fits the data perfectly well, giving a temperature dependent diffusivity according to $$\everymath{\displaystyle}\begin{array}{rcl}D(T) &=& 2.3 \times 10^{- 6}\\[5pt]&&{}\times \exp \biggl[ - \frac{( 215~\mathrm{kJ}\,\mathrm{mol}^{-1} )\!\times\! ( 1 + 0.176s^{2} )}{RT} \biggr]~\mathrm{m}^{2}\,\mathrm{s}^{-1}\end{array}$$

Growth and study of ultrathin insulating SiO2 and MgO layers on the ferromagnetic electrode surface

In this paper, we present the experimental results on the application of the pulsed laser deposition (PLD) method to form functional SiO2 and MgO layers in contact with Fe3Si and Fe ferromagnetic electrodes In situ X-ray photoelectron spectroscopy and low-energy ion scattering spectroscopy, in situ conversion electron Mossbauer spectroscopy and Rutherford backscattering and channeling of light ions were used to study the structural properties and morphology of formed ultrathin SiO2 and MgO layers, as well as the chemical and phase composition of Fe3 Si/SiO2 and Fe/MgO interfaces.

Characterisation of Granite Fractures From the In-Situ FEBEX Experiment (Grimsel, Switzerland): ossible Effects on Bentonite Colloid and Radionuclide Transport

AbstractThe FEBEX in-situ experiment, installed in 1997 at the Grimsel Test Site (GTS, Switzerland) 400 m depth under the Swiss Alps, simulates a high level radioactive waste repository (HLWR) emplaced in granite. Its initial aim was to study the performance of a bentonite engineered barrier but recently, two new boreholes were drilled in the granite to study the possible bentonite colloid formation and their migration in the granite.This study presents the characterization performed, at the micrometer scale, of the threemain water conductive fractures that were identified on the granite cores extracted from the newboreholes. These fractures are possible pathways for bentonite colloid transport (or retention),may be source of natural colloids and may condition colloid stability. The nuclear ion beamtechniques µ-Particle X-Ray Emission (µPIXE) and Rutherford Backscattering Spectrometry(RBS) were applied for visualizing and quantifying the elemental composition of the fracturessurface and of the surrounding micro-fractures, as support of the bentonite colloid analyses.

IBA of ZrO2:Yb/Si thin films produced by the spray pyrolysis method

A spray pyrolysis method was used to produce thin films of ZrO2 doped with different Yb concentrations on Si(100). The films of these ionic semiconductors have potential applications as solid electrolytes in modern ceramic fuel cells of second generation. The determination of the atomic composition of the films is very important because it strongly affects the chemical and thermal stability, as well as electrical properties of the films. A combination of two Ion Beam Analysis (IBA) methods was applied to obtain the atomic composition of the films. A nuclear reaction analysis (NRA) method using a low energy deuterium beam was applied to measure the oxygen content of the films. Heavy ion Rutherford backscattering (HI-RBS) method using a 12C3+ beam was applied to measure the Yb and Zr atomic profiles of the samples. X-ray diffraction (XRD) and ellipsometry were also employed to determine structural properties and refractive index of the films, respectively. The IBA, XRD and the ellipsometry supply a wide range of information about the film layers, which can be used for qualification as well as for feedback to the films production.

Heavy ion Rutherford backscattering spectrometry (HIRBS) study of barium diffusion in borosilicate glass

Diffusion of barium in borosilicate glasses containing sodium and calcium has been studied using heavy ion Rutherford backscattering spectrometry (HIRBS) using 30MeV 19F beam. A thin layer (25μg/cm2) of BaCl2 was vacuum evaporated on the polished surface of the glass samples which were then annealed at different temperatures (573–723K) and subsequently subjected to HIRBS measurements. It was observed that introduction of 10mole% of calcium in place of sodium results in increase in the activation energy of diffusion of barium by about 30%. This indicates that alkaline earth ions retard the diffusion process in borosilicate glass. The results corroborate the data obtained on diffusion of sodium by radiotracer method. The results have been explained in terms of the increasing rigidity of the glass network with introduction of alkaline earth ions.

Effect of AlN interlayer on incorporation efficiency of Al composition in AlGaN grown by MOVPE

We report the growth and characterization of the AlGaN on low temperature (LT) AlN interlayer (IL) and effect of AlN IL on incorporation efficiency of Al composition in the AlGaN. The AlGaN layers were grown on AlN ILs by metalorganic vapor phase epitaxy (MOVPE) and characterized by X-ray diffraction (XRD) and MeV He ion Rutherford backscattering spectrometry (RBS) and cathodoluminescence (CL), the results indicate that introduction of double AlN IL resulted in an increase in Al composition incorporation efficiency.

Study on structure of AlGaN on AlN interlayer by synchrotron radiation XRD and RBS

The AlGaN samples have been grown on AlN interlayer (IL) by metalorganic vapor phase epitaxy (MOVPE). The effects of AlN interlayer (IL) on improvement of crystalline quality of AlGaN and Al incorporation efficiency were investigated. The samples were characterized by synchrotron radiation X-ray diffraction (XRD) and MeV He ion Rutherford backscattering spectrometry (RBS). The AlN IL played a role in suppressing edge threading dislocations (TDs) and enhancing the screw ones. It also changed the state of stress in AlGaN from tension to compression. Crack-free AlGaN films were grown successfully by inserting AlN IL.

Search for ferromagnetism in conductive Nb:SrTiO3 with magnetic transition element (Cr, Co, Fe, Mn) dopants

Thin films of (0.5%, 1%) Nb:SrTiO3 dilutely doped with (2at.%) magnetic transition elements (Cr, Co, Fe, Mn) are examined for ferromagnetism. X-ray diffraction, Rutherford backscattering ion channeling, scanning transmission electron microscopy Z-contrast imaging, and electron energy loss spectroscopy techniques establish high crystalline quality of the films with no impurity phase(s) and highly uniform dopant distribution. Although the film conductivity improves dramatically by Nb doping, no ferromagnetism is found in any of our samples over the temperature range of 365 down to 5K. This is contrasted to the case of ferromagnetism reported in cobalt doped (La,Sr)TiO3.

Effect of glass composition on diffusion of cesium in borosilicate glass

Summary Heavy ion Rutherford backscattering spectrometry, with 30 MeV 19F beam, has been used to study the diffusion of cesium in borosilicate glasses of different compositions. The coefficient of cesium diffusion in borosilicate glass was obtained by analyzing the depth profile of cesium in samples annealed at different temperatures in the range of 100-350 °C. The activation energy of diffusion of cesium was found to be in the range of 9-22 kJ/mol, indicating the inter-diffusion between the cesium and sodium as the mechanism of the diffusion process. The activation energy was found to decrease with increasing sodium content of the glass, indicating that the alkali metal ion diffusion is governed by the interaction between the jumping ion and the dipole field around the oxygen ions.

Surface Stoichiometry and Structural Properties of Copper‐Containing Sol–Gel SiO2 Films

AbstractSummary: A study of the surface stoichiometry and structural properties of composite, copper‐containing, silica thin films (Cu:SiO2) is presented. The films are prepared on glass substrates by a sol–gel route. The coatings deposited by a dipping process are thermally treated under oxidative and subsequently reductive conditions up to 500 °C for metal nanoparticle formation. The coating structure, the nanoparticle formation, the copper diffusion, and the chemical composition of the surface are investigated using X‐ray diffraction (XRD), UV‐vis spectroscopy, heavy ion rutherford backscattering spectroscopy (HIRBS), and X‐ray photoelectron spectroscopy (XPS) as analytical methods.HIRBS spectrum, showing the Cu distribution of samples studied: a) as prepared, b) after heating under oxidative, and c) after heating under reductive conditions, using 12C3+ ions at 10 MeV.imageHIRBS spectrum, showing the Cu distribution of samples studied: a) as prepared, b) after heating under oxidative, and c) after heating under reductive conditions, using 12C3+ ions at 10 MeV.

Structure and kinetics of formation and decomposition of corrosion layers formed on lithium compounds exposed to atmospheric gases

A thorough review of the literature on the structure, growth kinetics and decomposition of (corrosion) layers formed upon the reaction of LiH and other lithium compounds with atmospheric gases, particularly water, suggests that simple models, consistent with thermodynamics, similar to those postulated to explain corrosion in other materials, can effectively explain all of the data. For example, data from a host of techniques, including calorimetry, microbalance, X-ray photoelectron spectroscopy, secondary ion mass spectrometry and Rutherford back-scattering, indicate that on LiH the corrosion layer formed upon water exposure grows at a nearly constant rate and consists of two layers, a very thin layer of Li2O sandwiched between LiOH and the original LiH ('tri-layer' model). These form during the reaction of water at two subsurface interfaces: LiH/Li2O and Li2O/LiOH. These reactions result in the release of hydrogen (2LiH+H2O→Li2O+2H2), and the growth of the LiOH layer (Li2O+H2O→2LiOH). Alternative models found in the literature, which include features such as the existence of LiOH/LiH interfaces, are shown to be inconsistent with thermodynamics. It is also shown that confusion regarding the mechanism of decomposition of LiOH upon heating results from a failure to account for the fact that the decomposition process of LiOH 'on top of' LiH is fundamentally different from that of pure LiOH. In fact, thermodynamics clearly predicts that even at room temperature the trilayer model is not stable, and should eventually decompose to two layers, Li2O on top of LiH. Thus, the layer of LiOH formed on top of LiH, produced for example for surface studies, is in fact composed of both LiOH and Li2O on top of LiH (i.e. the 'tri-layer' structure) and this structure will gradually decompose, releasing hydrogen, even at room temperature. This process will lead eventually to the simpler structure Li2O/LiH. In contrast, pure LiOH is stable except at temperatures above 400 K even in the driest environments. Finally, recent data show a 'barrier layer' will form during exposure of LiH to a gas containing both CO2 and water. Once fully formed (∼1 μm thickness), this barrier effectively prevents the attack of LiH by water.

Study of cesium diffusion in borosilicate glass by heavy ion Rutherford backscattering spectrometry

Abstract Diffusion of cesium in borosilicate glass has been studied by heavy ion Rutherford backscattering spectrometry (HIRBS) technique using 30 MeV 19F beam. Analysis of glass samples annealed at different temperatures for 12 h duration has been used to determine the activation energy of diffusion of cesium in borosilicate glass, which is considered as one of the suitable matrices for vitrification of the high level radioactive waste. Diffusion coefficients show Arrhenius behaviour in the temperature range 473–673 K. The activation energy for diffusion is found to be 22.2 ± 3.6 kJ/mol.

Energy and dose characteristics of ion bombardment during pulsed laser deposition of thin films under pulsed electric field

Experiments on pulsed laser deposition of Fe films on Si substrates were performed with the aim to analyze the role of factors determining the formation of an energy spectrum and a dose of ions bombarding the film in strong pulsed electric fields. The amplitude of the high-voltage pulse (−40kV) applied to the substrate and the laser fluence at the Fe target were fixed during the deposition. Owing to the high laser fluence (8J∕cm2) at a relatively low power (20mJ), the ionization of the laser plume was high, but the Fe vapor pressure near the substrate was low enough to avoid arcing. Electric signals from a target exposed to laser radiation were measured under different conditions (at different delay times) of application of electric pulses. The Si(100) substrates were analyzed using Rutherford ion backscattering∕channeling spectrometry. The ion implantation dose occurred to be the highest if the high-voltage pulse was applied at a moment of time when the ion component of the plume approached the substrate. In this case, the implanted ions had the highest energy determined by the amplitude of the electric pulse. An advance or delay in applying a high-voltage pulse caused the ion dose and energy to decrease. A physical model incorporating three possible modes of ion implantation was proposed for the interpretation of the experimental results. If a laser plume was formed in the external field, ions were accelerated from the front of the dense plasma, and the ion current depended on the gas-dynamic expansion of the plume. The application of a high-voltage pulse, at the instant when the front approached the substrate, maintained the mode that was characteristic of the traditional plasma immersion ion implantation, and the ion current was governed by the dynamics of the plasma sheath in the substrate-to-target gap. In the case of an extremely late application of a high-voltage pulse, ions retained in the entire volume of the experimental chamber (as a result of the laser-plume expansion) are involved in the implantation process. Therefore, the spread in implanted-ion energies depends on the configuration of the electric field inside the chamber.

Nanocomposite-like structure in an epitaxial CaCu3Ti4O12 film on LaAlO3 (001)

We report the detailed microstructural study of a CaCu3Ti4O12 (CCTO) thin film using transmission electron microscopy (TEM). The CCTO thin film studied in this work was deposited on a (001)-oriented LaAlO3 (LAO) substrate by pulsed-laser ablation and has a high dielectric constant of about 104 at 1 MHz at room temperature; however, the mechanism for such a dielectric property is not yet understood. Plan-view TEM studies show that the CCTO samples have orthogonal domain structures with the edge nearly parallel to either the [100] or the [010] direction of the CCTO. A minor anatase TiO2 phase was found at the domain boundaries. The CCTO and the TiO2 phases are separated by an amorphous-like layer that has a thickness of several nanometres. Cross-sectional TEM studies reveal that both CCTO and TiO2 in the films are c axis oriented with a very sharp interface to the LAO-(001) substrate and possess a unique crystallographic orientation relationship of (001) CCTO //(001)TiO 2 //(001) LAO and [100] CCTO //[100] TiO 2 //[100] LAO. The Rutherford back-scattering ion chanelling studies suggest a composition of Ca1.5Cu3Ti5.5O16 for the film, in which the extra calcium, titanium and oxygen form the anatase TiO2 phase and amorphous calcium oxide layer that separates the CCTO and TiO2 phases. Such nanocomposite-like structures may provide an important clue to the mechanism of the dielectric property of these films.

Synthesis of ternary SiGeSn semiconductors on Si(100) via SnxGe1−x buffer layers

Single-phase Si1−x−yGexSny alloys with random diamond cubic structures are created on Si(100) via ultrahigh vacuum chemical vapor deposition reactions of SnD4 with SiH3GeH3 at 350 °C. Commensurate heteroepitaxy is facilitated by Ge1−xSnx buffer layers, which act as templates that can conform structurally and absorb the differential strain imposed by the more rigid Si and Si–Ge–Sn materials. The crystal structure, elemental distribution and morphological properties of the Si1−x−yGexSny/Ge1−xSnx heterostructures are characterized by high-resolution electron microscopy, including electron energy loss nanospectroscopy, x-ray diffraction (rocking curves) and atomic force microscopy. These techniques demonstrate growth of perfectly epitaxial, uniform and highly aligned layers with atomically smooth surfaces and monocrystalline structures that have lattice constants close to that of Ge. Rutherford backscattering ion channeling shows that the constituent elements occupy random substitutional sites in the same average diamond cubic lattice and the Raman shifts are consistent with the lattice expansion produced by the Sn incorporation into SiGe tetrahedral sites.

Compositionally-tuned epitaxial cubic MgxZn1−xO on Si(100) for deep ultraviolet photodetectors

We report on the epitaxial growth of wide-band-gap cubic-phase MgxZn1−xO thin films on Si(100) by pulsed-laser deposition and fabrication of oxide-semiconductor-based ultraviolet photodetectors. The challenges of large lattice and thermal expansion mismatch between Si and MgxZn1−xO have been overcome by using a thin SrTiO3 buffer layer. The heteroepitaxy of cubic-phase MgxZn1−xO on Si was established with epitaxial relationship of MgxZn1−xO(100)//SrTiO3(100)//Si(100) and MgxZn1−xO[100]//SrTiO3[100]//Si[110]. The minimum yield of the Rutherford backscattering ion channeling in MgxZn1−xO layer was only 4%, indicating good crystalline quality of the film. Smooth surface morphology with rms roughness of 0.6 nm was observed using atomic force microscopy. Photodetectors fabricated on Mg0.68Zn0.32O/SrTiO3/Si show peak photoresponse at 225 nm, which is in the deep UV region.

Three-step amorphisation process in ion-implanted GaN at 15 K

GaN layers were implanted at 15 K with 150 keV O, 300 keV Ar or 800 keV Xe ions. The subsequent damage analysis was performed by Rutherford backscattering of He ions in channelling configuration at the same temperature. At this low temperature thermal effects can be widely excluded. However, the dependence of the damage concentration on the ion fluence suggests that the damage evolution in GaN is dominated by a pronounced recombination of the primarily produced defects within the collision cascades. Furthermore, a strong influence of the ions themselves has to be assumed in order to understand the experimental results. Such effects occur already at rather low ion fluences. Our results indicate an amorphisation of GaN proceeding in three steps.

Study of Antibacterial Composite Cu/SiO2 Thin Coatings

In the present work, composite copper containing silicate thin coatings (Cu/SiO2) were prepared on glass substrates by the sol-gel route. The preparation process included hydrolysis and subsequent polycondensation of corresponding alkoxide under refluxing and addition of soluble salt of antibacterial metal to the resulting sol. The coatings deposited by dipping process, were thermally treated in oxidative and reductive conditions up to 500°C for metal nanoparticles formation. The coating structure and the nanoparticles formation were studied by the X-ray Diffraction (XRD), UV-VIS and Heavy Ion Rutherford Backscattering (HIRBS) Spectroscopies. The antibacterial activity against Escherichia Coli was examined by the so-called antibacterial-drop test. The possible correlation between the layer interdiffusion after the thermal treatment and the antibacterial activity was considered and analyzed. The coatings exhibited a high antibacterial activity, which was enhanced with the increase of the metal concentration and was decreased with the increase of temperature of thermal treatment and metal nanoparticles formation.

SIMS and RBS study of thermally annealed Pd/β-SiC interfaces

The Pd/β-SiC interfaces were studied using secondary ion mass spectrometry (SIMS) and Rutherford backscattering spectrometry (RBS). This was done with the intent of clarifying any reaction or inter-diffusion at the interface upon prolonged annealing at different temperatures in air. SIMS study indicates that the interface is stable up to 400 °C for at least 12 h. However, at 800 °C, the interface was completely degraded with significant inter-diffusion of palladium and silicon. The RBS study confirms the SIMS observations.

A universal ion implantation model for all species into single-crystal silicon

A physically based model for ion implantation of any species into single crystal silicon has been developed, tested and implemented in the ion implant simulator, UT-MARLOWE. In this model, an interpolation scheme, based on mathematical properties of ion-target interatomic potential, was employed and implemented to calculate the scattering process. Using this scheme, the resulting energy, direction and momentum of the ion and target can be derived from the existing scattering tables of UT-MARLOWE without calculating the entire scattering process. The method has advantages in terms of both accuracy and computational efficiency, as well as significantly reduced cost of code development. The impurity profiles and damage profiles predicted by the model simulations have been compared with secondary ion mass spectroscopy (SIMS) and Rutherford backscattering spectrometry (RBS), and excellent agreement with experimental data has been achieved.